Why life possible on earth

Other planets are colder still. Earth has water! Water is considered to be the most important chemical necessary for life. It contains the oxygen needed for life. Other liquids can contain poisonous elements. Water doesn't burn skin like liquids containing acids do , it is drinkable, and it allows life-providing molecules to move around easily.

Other moons in the Solar System, such as Europa , a moon of Jupiter , are believed to have oceans of water under its icy surface. Scientists believe that the presence of water on other objects in the solar system greatly increases the chances of life existing on them. Water on Earth is abundant and can be found in its three states of matter. It can be frozen, taking the form of ice. It can be liquid, seen in seas and oceans and lakes. It can also be a gas, seen as clouds. In the picture below, we can see water in its three states; a solid, a liquid and a gas.

The blue glow at the top of the Earth is the planet's thin atmosphere. All planets receive light from the Sun , but no planet uses it as usefully as Earth. Trees and plants on the planet produce oxygen through a process called photosynthesis. Plants need the Sun to grow.

Look at plants in windows and notice how they usually seem to grow towards the Sun. Try growing a plant in a dark room and in a light room. Notice which one grows quicker. The one which has grown quickest is the one which also produces more oxygen. It is believed that if we were able to get plants to grow on another planet, such as Mars , they would begin putting oxygen into the planet's atmosphere and increase the possibility of life.

Another principle, that of mediocrity, suggests that there is nothing special about our galaxy or Earth. And yet, so far, not only are we unaware of the existence of anyone else , but we have yet to find a planet similar to our own.

Life is far from inevitable , say scientists, and our presence here may simply be the result of a series of lucky events, like prizes from a cosmic lottery that many other planets missed out on at some point in their history. The existence of life on Earth rests on five main pillars: the distance from the Sun, neither too close nor too far away, just enough for liquid water; the magnetic core, which protects the atmosphere from the drag of the solar wind and life from cosmic radiation; the atmosphere itself, whose greenhouse effect prevents water from freezing; water, naturally, the universal solvent of life; and finally oxygen, which allows us to breathe.

But unlike a recipe, these ingredients are not entirely independent of each other. And, above all, as in the preparation of any dish, only if they are combined in the right order and cooked in the correct way do we obtain the result that makes it possible for us to be here today. About 4. In just a few million years, the Solar System looked much like it does today, but between Venus and Mars there was not one planet, but two; according to the most widely accepted hypothesis, the subsequent collision between the Proto-Earth and Theia, another Mars-sized object, gave rise to our Earth and its Moon some 4.

These figures are obtained by studying the isotope ratios of elements such as lead, which is produced by the radioactive decay of uranium over billions of years. Our other neighbour, Mars, is an example of how the lack of a magnetic shield to protect the planet from the buffeting of the solar wind, which the little red planet lost as its core cooled , eventually stripped it of its atmosphere. But for all this to progress, the presence of water is essential.

It has traditionally been proposed that the fiery early Earth was a dry ball and that water arrived on board the meteorites and comets that fell on the planet in its early days. Thus, about 4. Due to the friction generated between a meteor and the atmospheric gases, most meteors burn up before hitting Earth's surface as a meteorite. The Earth from space A hurricane seen from space Earth rotates on an imaginary axis which is tilted at a The rotation is what causes the change from day to night.

The tilt is what determines our change in seasons. If the Earth was not tilted, we would have the same season all year long.

Earth has a core of molten iron-nickel. The rapid spin of the Earth along with the liquid, hot metallic core causes a magnetic field to surround the Earth. This magnetic field traps the charged particles which are hurled at the Earth by the Sun during solar wind activity.

David Wolf! We do know that life as we understand it requires very special conditions to exist. In fact, many scientists believe that these conditions exist elsewhere and offer the possibility for life beyond just our Earth. These may be very simple organisms such as bacteria or even more complex life such as plants and animals. All living things need some sort of food, water, the right atmosphere and temperature.

Even the strength of gravity determines the form of our bodies such as our bones and muscle strength. All living things on earth have adapted to our atmosphere, which means all living things need our mix of atmospheric gases. Life elsewhere would be specifically adapted to their own conditions. Water is a really important ingredient to sustain the kind of life we know on Earth. Both plants and animals require water for survival.

Planet Earth is very special because it contains so much water in liquid form. One of things that the Mars Rover, Curiosity, is looking for is the presence of water now or evidence that it existed in the past on Mars. It appears that Mars did have lots of liquid water at one time. Conditions might have been right on Mars to support life. For living things the correct temperature is really important. Most life on earth lives in warm to moderate temperatures.

So, there still might be life on other planets, or even the moons of other planets, but it would probably be very different than life on Earth! These other possible forms of life would be very far away so they are not something to worry about.

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